Electrically variable transmission having three planetary gear sets, a stationary member and three fixed interconnections

ABSTRACT

The electrically variable transmission family provides low-content, low-cost electrically variable transmission mechanisms including first, second and third differential gear sets, a battery, two electric machines serving interchangeably as motors or generators, up to six selectable torque-transfer devices, and possibly a dog clutch. The selectable torque transfer devices are engaged to yield an EVT with a continuously variable range of speeds (including reverse) and mechanically fixed forward speed ratios. The torque transfer devices and the first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.

TECHNICAL FIELD

The present invention relates to electrically variable transmissionswith selective operation both in power-split variable speed ratio rangesand in fixed speed ratios, and having three planetary gear sets, twomotor/generators and up to six torque transfer devices.

BACKGROUND OF THE INVENTION

Internal combustion engines, particularly those of the reciprocatingpiston type, currently propel most vehicles. Such engines are relativelyefficient, compact, lightweight, and inexpensive mechanisms by which toconvert highly concentrated energy in the form of fuel into usefulmechanical power. A novel transmission system, which can be used withinternal combustion engines and which can reduce fuel consumption andthe emissions of pollutants, may be of great benefit to the public.

The wide variation in the demands that vehicles typically place oninternal combustion engines increases fuel consumption and emissionsbeyond the ideal case for such engines. Typically, a vehicle ispropelled by such an engine, which is started from a cold state by asmall electric motor and relatively small electric storage batteries,then quickly placed under the loads from propulsion and accessoryequipment. Such an engine is also operated through a wide range ofspeeds and a wide range of loads and typically at an average ofapproximately a fifth of its maximum power output.

A vehicle transmission typically delivers mechanical power from anengine to the remainder of a drive system, such as fixed final drivegearing, axles and wheels. A typical mechanical transmission allows somefreedom in engine operation, usually through alternate selection of fiveor six different drive ratios, a neutral selection that allows theengine to operate accessories with the vehicle stationary, and clutchesor a torque converter for smooth transitions between driving ratios andto start the vehicle from rest with the engine turning. Transmissiongear selection typically allows power from the engine to be delivered tothe rest of the drive system with a ratio of torque multiplication andspeed reduction, with a ratio of torque reduction and speedmultiplication known as overdrive, or with a reverse ratio.

An electric generator can transform mechanical power from the engineinto electrical power, and an electric motor can transform that electricpower back into mechanical power at different torques and speeds for theremainder of the vehicle drive system. This arrangement allows acontinuous variation in the ratio of torque and speed between engine andthe remainder of the drive system, within the limits of the electricmachinery. An electric storage battery used as a source of power forpropulsion may be added to this arrangement, forming a series hybridelectric drive system.

The series hybrid system allows the engine to operate with someindependence from the torque, speed and power required to propel avehicle, so the engine may be controlled for improved emissions andefficiency. This system allows the electric machine attached to theengine to act as a motor to start the engine. This system also allowsthe electric machine attached to the remainder of the drive train to actas a generator, recovering energy from slowing the vehicle into thebattery by regenerative braking. A series electric drive suffers fromthe weight and cost of sufficient electric machinery to transform all ofthe engine power from mechanical to electrical in the generator and fromelectrical to mechanical in the drive motor, and from the useful energylost in these conversions.

A power-split transmission can use what is commonly understood to be“differential gearing” to achieve a continuously variable torque andspeed ratio between input and output. An electrically variabletransmission can use differential gearing to send a fraction of itstransmitted power through a pair of electric motor/generators. Theremainder of its power flows through another, parallel path that is allmechanical and direct, of fixed ratio, or alternatively selectable.

One form of differential gearing, as is well known to those skilled inthis art, may constitute a planetary gear set. Planetary gearing isusually the preferred embodiment employed in differentially gearedinventions, with the advantages of compactness and different torque andspeed ratios among all members of the planetary gear set. However, it ispossible to construct this invention without planetary gears, as byusing bevel gears or other gears in an arrangement where the rotationalspeed of at least one element of a gear set is always a weighted averageof speeds of two other elements.

A hybrid electric vehicle transmission system also includes one or moreelectric energy storage devices. The typical device is a chemicalelectric storage battery, but capacitive or mechanical devices, such asan electrically driven flywheel, may also be included. Electric energystorage allows the mechanical output power from the transmission systemto the vehicle to vary from the mechanical input power from the engineto the transmission system. The battery or other device also allows forengine starting with the transmission system and for regenerativevehicle braking.

An electrically variable transmission in a vehicle can simply transmitmechanical power from an engine input to a final drive output. To do so,the electric power produced by one motor/generator balances theelectrical losses and the electric power consumed by the othermotor/generator. By using the above-referenced electrical storagebattery, the electric power generated by one motor/generator can begreater than or less than the electric power consumed by the other.Electric power from the battery can sometimes allow bothmotor/generators to act as motors, especially to assist the engine withvehicle acceleration. Both motors can sometimes act as generators torecharge the battery, especially in regenerative vehicle braking.

A successful substitute for the series hybrid transmission is thetwo-range, input-split and compound-split electrically variabletransmission now produced for transit buses, as disclosed in U.S. Pat.No. 5,931,757, issued Aug. 3, 1999, to Michael Roland Schmidt, commonlyassigned with the present application, and hereby incorporated byreference in its entirety. Such a transmission utilizes an input meansto receive power from the vehicle engine and a power output means todeliver power to drive the vehicle. First and second motor/generatorsare connected to an energy storage device, such as a battery, so thatthe energy storage device can accept power from, and supply power to,the first and second motor/generators. A control unit regulates powerflow among the energy storage device and the motor/generators as well asbetween the first and second motor/generators.

Operation in first or second variable-speed-ratio modes of operation maybe selectively achieved by using clutches in the nature of first andsecond torque transfer devices. In the first mode, an input-power-splitspeed ratio range is formed by the application of the first clutch, andthe output speed of the transmission is proportional to the speed of onemotor/generator. In the second mode, a compound-power-split speed ratiorange is formed by the application of the second clutch, and the outputspeed of the transmission is not proportional to the speeds of either ofthe motor/generators, but is an algebraic linear combination of thespeeds of the two motor/generators. Operation at a fixed transmissionspeed ratio may be selectively achieved by the application of both ofthe clutches. Operation of the transmission in a neutral mode may beselectively achieved by releasing both clutches, decoupling the engineand both electric motor/generators from the transmission output. Thetransmission incorporates at least one mechanical point in its firstmode of operation and at least two mechanical points in its second modeof operation.

U.S. Pat. No. 6,527,658, issued Mar. 4, 2003 to Holmes et al, commonlyassigned with the present application, and hereby incorporated byreference in its entirety, discloses an electrically variabletransmission utilizing two planetary gear sets, two motor/generators andtwo clutches to provide input split, compound split, neutral and reversemodes of operation. Both planetary gear sets may be simple, or one maybe individually compounded. An electrical control member regulates powerflow among an energy storage device and the two motor/generators. Thistransmission provides two ranges or modes of electrically variabletransmission (EVT) operation, selectively providing an input-power-splitspeed ratio range and a compound-power-split speed ratio range. Onefixed speed ratio can also be selectively achieved.

SUMMARY OF THE INVENTION

The present invention provides a family of electrically variabletransmissions offering several advantages over conventional automatictransmissions for use in hybrid vehicles, including improved vehicleacceleration performance, improved fuel economy via regenerative brakingand electric-only idling and launch, and an attractive marketingfeature. An object of the invention is to provide the best possibleenergy efficiency and emissions for a given engine. In addition, optimalperformance, capacity, package size, and ratio coverage for thetransmission are sought.

The electrically variable transmission family of the present inventionprovides low-content, low-cost electrically variable transmissionmechanisms including first, second and third differential gear sets, abattery, two electric machines serving interchangeably as motors orgenerators, and up to six selectable torque-transfer devices.Preferably, the differential gear sets are planetary gear sets, such assimple or compound (including Ravigneaux) gear sets, but other geararrangements may be implemented, such as bevel gears or differentialgearing to an offset axis.

In this description, the first, second, or third planetary gear sets maybe counted first to third in any order (i.e., left to right, right toleft, etc.).

Each of the three planetary gear sets has three members. The first,second or third member of each planetary gear set can be any one of asun gear, ring gear or carrier member, or alternatively a pinion.

Each carrier member can be either a single-pinion carrier member(simple) or a double-pinion carrier member (compound).

The input shaft is continuously connected with at least one member ofthe planetary gear sets. The output shaft is continuously connected withanother member of the planetary gear sets.

A first interconnecting member continuously connects a first member ofthe first planetary gear set with the first member of the secondplanetary gear set.

A second interconnecting member continuously connects the second memberof the first planetary gear set with a first member of the thirdplanetary gear set.

A third interconnecting member continuously connects a second member ofthe second planetary gear set with the second member of the thirdplanetary gear set.

A fourth interconnecting member continuously connects a member of thefirst planetary gear set with a stationary member (transmissionhousing/casing).

A first torque transfer device selectively connects a member of thefirst planetary gear set with a member of the second planetary gear set.

A second torque transmitting device is connected in parallel with one ofthe motor/generators for selectively preventing rotation thereof.

An optional third torque transfer device selectively connects a memberof the second or third planetary gear set with another member of thethird planetary gear set or with the stationary member(ground/transmission case).

An optional third or fourth torque transmitting device selectivelyconnects a member of the first or third planetary gear set with thestationary member.

Optional fourth, fifth, and sixth torque transmitting devicesselectively connect members of the gear sets with one of themotor/generators or with ground in parallel with one of themotor/generators for selectively preventing rotation of themotor/generator.

The first motor/generator is mounted to the transmission case and isconnected either continuously to a member of the first, second or thirdplanetary gear set or selectively via a dog clutch (or equivalently by apair of clutches) to a member of the first, second or third planetarygear set. The first motor/generator may also incorporate offset gearing.

The second motor/generator is mounted to the transmission case (orground) and is continuously connected to a member of the second or thirdplanetary gear set. The second motor/generator connection mayincorporate offset gearing.

The selectable torque transfer devices are engaged in combinations ofzero, one or two to yield an EVT with a continuously variable range ofspeeds (including reverse) and up to four mechanically fixed forwardspeed ratios. A “fixed speed ratio” is an operating condition in whichthe mechanical power input to the transmission is transmittedmechanically to the output, and no power flow (i.e. almost zero) ispresent in the motor/generators. An electrically variable transmissionthat may selectively achieve several fixed speed ratios for operationnear full engine power can be smaller and lighter for a given maximumcapacity. Fixed ratio operation may also result in lower fuelconsumption when operating under conditions where engine speed canapproach its optimum without using the motor/generators. A variety offixed speed ratios and variable ratio spreads can be realized bysuitably selecting the tooth ratios of the planetary gear sets.

Each embodiment of the electrically variable transmission familydisclosed has an architecture in which neither the transmission inputnor output is directly connected to a motor/generator. This allows for areduction in the size and cost of the electric motor/generators requiredto achieve the desired vehicle performance.

The torque transfer devices, and the first and second motor/generatorsare operable to provide five operating modes in the electricallyvariable transmission, including battery reverse mode, EVT reverse mode,reverse and forward launch modes, continuously variable transmissionrange mode, and fixed ratio mode.

The above features and advantages, and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation of a powertrain including anelectrically variable transmission incorporating a family member of thepresent invention;

FIG. 1 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 1a;

FIG. 2 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 2 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 2a;

FIG. 3 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 3 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 3a;

FIG. 4 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 4 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 4a;

FIG. 5 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 5 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 5a;

FIG. 6 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 6 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 6a;

FIG. 7 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 7 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 7a;

FIG. 8 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 8 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 8a;

FIG. 9 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 9 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 9a;

FIG. 10 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 10 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 10 a;

FIG. 11 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 11 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 11 a;

FIG. 12 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 12 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 12 a;

FIG. 13 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 13 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 13 a;

FIG. 14 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention; and

FIG. 14 b is an operating mode table and fixed ratio mode tabledepicting some of the operating characteristics of the powertrain shownin FIG. 14 a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 a, a powertrain 10 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission (EVT), designated generally by thenumeral 14. Transmission 14 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 14.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission.

In the embodiment depicted the engine 12 may be a fossil fuel engine,such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM).

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 14. Anoutput member 19 of the transmission 14 is connected to a final drive16.

The transmission 14 utilizes three differential gear sets, preferably inthe nature of planetary gear sets 20, 30 and 40. The planetary gear set20 employs an outer gear member 24, typically designated as the ringgear. The ring gear member 24 circumscribes an inner gear member 22,typically designated as the sun gear. A carrier member 26 rotatablysupports a plurality of planet gears 27 such that each planet gear 27meshingly engages both the outer, ring gear member 24 and the inner, sungear member 22 of the first planetary gear set 20.

The planetary gear set 30 also has an outer gear member 34, often alsodesignated as the ring gear, that circumscribes an inner gear member 32,also often designated as the sun gear member. A plurality of planetgears 37 are also rotatably mounted in a carrier member 36 such thateach planet gear member 37 simultaneously, and meshingly, engages boththe outer, ring gear member 34 and the inner, sun gear member 32 of theplanetary gear set 30.

The planetary gear set 40 also has an outer gear member 44, often alsodesignated as the ring gear, that circumscribes an inner gear member 42,also often designated as the sun gear. A plurality of planet gears 47are also rotatably mounted in a carrier member 46 such that each planetgear member 47 simultaneously, and meshingly, engages both the outer,ring gear member 44 and the inner, sun gear member 42 of the planetarygear set 40.

A first interconnecting member 70 continuously connects the carriermember 26 of the planetary gear set 20 with the ring gear member 34 ofthe planetary gear set 30. A second interconnecting member 72continuously connects the sun gear member 22 of the planetary gear set20 with the carrier member 46 of the planetary gear set 40. A thirdinterconnecting member 74 continuously connects the sun gear member 32of the planetary gear set 30 with the sun gear member 42 of theplanetary gear set 40. A fourth interconnecting member 76 continuouslyconnects the ring gear member 24 with the transmission housing 60.

The first preferred embodiment 10 also incorporates first and secondmotor/generators 80 and 82, respectively. The stator of the firstmotor/generator 80 is secured to the transmission housing 60. The rotorof the first motor/generator 80 is secured to the sun gear member 42 ofthe planetary gear set 40.

The stator of the second motor/generator 82 is also secured to thetransmission housing 60. The rotor of the second motor/generator 82 isselectively connectable to the carrier member 46 or the ring gear member44 of the planetary gear set 40 via engagement of the clutch 54 or 55,respectively.

A first torque transfer device, such as clutch 50, selectively connectsthe ring gear member 34 of the planetary gear set 30 with the carriermember 36 of the planetary gear set 30. A second torque transfer device,such as clutch 52, selectively connects the sun gear member 42 of theplanetary gear set 40 with the carrier member 46 of the planetary gearset 40. A third torque transfer device, such as clutch 54, selectivelyconnects the carrier member 46 of the planetary gear set 40 with themotor/generator 82. A fourth torque transmitting device, such as clutch55, selectively connects the ring gear member 44 of the planetary gearset with the motor/generator 82. A fifth torque transfer device, such asthe brake 56, is connected in parallel with the motor/generator 80 forselectively braking rotation thereof. A sixth torque transmittingdevice, such as brake 57, is connected in parallel with themotor/generator 82 for selectively braking rotation thereof. The first,second, third, fourth, fifth and sixth torque transfer devices 50, 52,54, 55, 56 and 57 are employed to assist in the selection of theoperational modes of the hybrid transmission 14, as will be hereinaftermore fully explained.

The input drive member 17 is continuously connected with the carriermember 36 of the planetary gear set 30. The output drive member 19 ofthe transmission 14 is secured to the carrier member 26 of the planetarygear set 20.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 1 a, that the transmission 14 selectively receives power fromthe engine 12. The hybrid transmission also receives power from anelectric power source 86, which is operably connected to a controller88. The electric power source 86 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

General Operating Considerations

One of the primary control devices is a well known drive range selector(not shown) that directs an electronic control unit (the ECU 88) toconfigure the transmission for either the park, reverse, neutral, orforward drive range. The second and third primary control devicesconstitute an accelerator pedal (not shown) and a brake pedal (also notshown). The information obtained by the ECU from these three primarycontrol sources is designated as the “operator demand.” The ECU alsoobtains information from a plurality of sensors (input as well asoutput) as to the status of: the torque transfer devices (either appliedor released); the engine output torque; the unified battery, orbatteries, capacity level; and, the temperatures of selected vehicularcomponents. The ECU determines what is required and then manipulates theselectively operated components of, or associated with, the transmissionappropriately to respond to the operator demand.

The invention may use simple or compound planetary gear sets. In asimple planetary gear set a single set of planet gears are normallysupported for rotation on a carrier member that is itself rotatable.

In a simple planetary gear set, when the sun gear is held stationary andpower is applied to the ring gear of a simple planetary gear set, theplanet gears rotate in response to the power applied to the ring gearand thus “walk” circumferentially about the fixed sun gear to effectrotation of the carrier member in the same direction as the direction inwhich the ring gear is being rotated.

When any two members of a simple planetary gear set rotate in the samedirection and at the same speed, the third member is forced to turn atthe same speed, and in the same direction. For example, when the sungear and the ring gear rotate in the same direction, and at the samespeed, the planet gears do not rotate about their own axes but ratheract as wedges to lock the entire unit together to effect what is knownas direct drive. That is, the carrier member rotates with the sun andring gears.

However, when the two gear members rotate in the same direction, but atdifferent speeds, the direction in which the third gear member rotatesmay often be determined simply by visual analysis, but in manysituations the direction will not be obvious and can only be accuratelydetermined by knowing the number of teeth present on all the gearmembers of the planetary gear set.

Whenever the carrier member is restrained from spinning freely, andpower is applied to either the sun gear or the ring gear, the planetgear members act as idlers. In that way the driven member is rotated inthe opposite direction as the drive member. Thus, in many transmissionarrangements when the reverse drive range is selected, a torque transferdevice serving as a brake is actuated frictionally to engage the carriermember and thereby restrain it against rotation so that power applied tothe sun gear will turn the ring gear in the opposite direction. Thus, ifthe ring gear is operatively connected to the drive wheels of a vehicle,such an arrangement is capable of reversing the rotational direction ofthe drive wheels, and thereby reversing the direction of the vehicleitself.

In a simple set of planetary gears, if any two rotational speeds of thesun gear, the planet carrier member, and the ring gear are known, thenthe speed of the third member can be determined using a simple rule. Therotational speed of the carrier member is always proportional to thespeeds of the sun and the ring, weighted by their respective numbers ofteeth. For example, a ring gear may have twice as many teeth as the sungear in the same set. The speed of the carrier member is then the sum oftwo-thirds the speed of the ring gear and one-third the speed of the sungear. If one of these three members rotates in an opposite direction,the arithmetic sign is negative for the speed of that member inmathematical calculations.

The torque on the sun gear, the carrier member, and the ring gear canalso be simply related to one another if this is done withoutconsideration of the masses of the gears, the acceleration of the gears,or friction within the gear set, all of which have a relatively minorinfluence in a well designed transmission. The torque applied to the sungear of a simple planetary gear set must balance the torque applied tothe ring gear, in proportion to the number of teeth on each of thesegears. For example, the torque applied to a ring gear with twice as manyteeth as the sun gear in that set must be twice that applied to the sungear, and must be applied in the same direction. The torque applied tothe carrier member must be equal in magnitude and opposite in directionto the sum of the torque on the sun gear and the torque on the ringgear.

In a compound planetary gear set, the utilization of inner and outersets of planet gears effects an exchange in the roles of the ring gearand the planet carrier member in comparison to a simple planetary gearset. For instance, if the sun gear is held stationary, the planetcarrier member will rotate in the same direction as the ring gear, butthe planet carrier member with inner and outer sets of planet gears willtravel faster than the ring gear, rather than slower.

In a compound planetary gear set having meshing inner and outer sets ofplanet gears the speed of the ring gear is proportional to the speeds ofthe sun gear and the planet carrier member, weighted by the number ofteeth on the sun gear and the number of teeth filled by the planetgears, respectively. For example, the difference between the ring andthe sun filled by the planet gears might be as many teeth as are on thesun gear in the same set. In that situation the speed of the ring gearwould be the sum of two-thirds the speed of the carrier member and onethird the speed of the sun. If the sun gear or the planet carrier memberrotates in an opposite direction, the arithmetic sign is negative forthat speed in mathematical calculations.

If the sun gear were to be held stationary, then a carrier member withinner and outer sets of planet gears will turn in the same direction asthe rotating ring gear of that set. On the other hand, if the sun gearwere to be held stationary and the carrier member were to be driven,then planet gears in the inner set that engage the sun gear roll, or“walk,” along the sun gear, turning in the same direction that thecarrier member is rotating. Pinion gears in the outer set that mesh withpinion gears in the inner set will turn in the opposite direction, thusforcing a meshing ring gear in the opposite direction, but only withrespect to the planet gears with which the ring gear is meshinglyengaged. The planet gears in the outer set are being carried along inthe direction of the carrier member. The effect of the rotation of thepinion gears in the outer set on their own axis and the greater effectof the orbital motion of the planet gears in the outer set due to themotion of the carrier member are combined, so the ring rotates in thesame direction as the carrier member, but not as fast as the carriermember.

If the carrier member in such a compound planetary gear set were to beheld stationary and the sun gear were to be rotated, then the ring gearwill rotate with less speed and in the same direction as the sun gear.If the ring gear of a simple planetary gear set is held stationary andthe sun gear is rotated, then the carrier member supporting a single setof planet gears will rotate with less speed and in the same direction asthe sun gear. Thus, one can readily observe the exchange in rolesbetween the carrier member and the ring gear that is caused by the useof inner and outer sets of planet gears which mesh with one another, incomparison with the usage of a single set of planet gears in a simpleplanetary gear set.

The normal action of an electrically variable transmission is totransmit mechanical power from the input to the output. As part of thistransmission action, one of its two motor/generators acts as a generatorof electrical power. The other motor/generator acts as a motor and usesthat electrical power. As the speed of the output increases from zero toa high speed, the two motor/generators 80, 82 gradually exchange rolesas generator and motor, and may do so more than once. These exchangestake place around mechanical points, where essentially all of the powerfrom input to output is transmitted mechanically and no substantialpower is transmitted electrically.

In a hybrid electrically variable transmission system, the battery 86may also supply power to the transmission or the transmission may supplypower to the battery. If the battery is supplying substantial electricpower to the transmission, such as for vehicle acceleration, then bothmotor/generators may act as motors. If the transmission is supplyingelectric power to the battery, such as for regenerative braking, bothmotor/generators may act as generators. Very near the mechanical pointsof operation, both motor/generators may also act as generators withsmall electrical power outputs, because of the electrical losses in thesystem.

Contrary to the normal action of the transmission, the transmission mayactually be used to transmit mechanical power from the output to theinput. This may be done in a vehicle to supplement the vehicle brakesand to enhance or to supplement regenerative braking of the vehicle,especially on long downward grades. If the power flow through thetransmission is reversed in this way, the roles of the motor/generatorswill then be reversed from those in normal action.

Specific Operating Considerations

Each of the embodiments described herein has up to sixteen functionalrequirements (corresponding with the 14 or 16 rows of each operatingmode table shown in the Figures) which may be grouped into fiveoperating modes. These five operating modes are described below and maybe best understood by referring to the respective operating mode tableaccompanying each transmission stick diagram, such as the operating modetables of FIG. 1 b, 2 b, 3 b, etc.

The first operating mode is the “battery reverse mode” which correspondswith the first row (Batt Rev) of each operating mode table, such as thatof FIG. 1 b. In this mode, the engine is off and the transmissionelement connected to the engine is not controlled by engine torque,though there may be some residual torque due to the rotational inertiaof the engine. The EVT is driven by one of the motor/generators usingenergy from the battery, causing the vehicle to move in reverse.Depending on the kinematic configuration, the other motor/generator mayor may not rotate in this mode, and may or may not transmit torque. Ifit does rotate, it is used to generate energy which is stored in thebattery. In the embodiment of FIG. 1 b, in the battery reverse mode, theclutch 55 is engaged, the generator 80 has a torque of −0.33, the motor82 has a torque of −1.00, and a torque ratio of −4.39 is achieved, byway of example. In each operating mode table an (M) next to a torquevalue in the motor/generator columns 80 and 82 indicates that themotor/generator is acting as a motor, and the absence of an (M)indicates that the motor/generator is acting as generator.

The second operating mode is the “EVT reverse mode” (or mechanicalreverse mode) which corresponds with the second row (EVT Rev) of eachoperating mode table, such as that of FIG. 1 b. In this mode, the EVT isdriven by the engine and by one of the motor/generators. The othermotor/generator operates in generator mode and transfers 100% of thegenerated energy back to the driving motor. The net effect is to drivethe vehicle in reverse. Referring to FIG. 1 b, for example, in the EVTreverse mode, the clutch 55 is engaged, the generator 80 has a torque of−1.01 units, the motor 82 has a torque of −2.04 units, and an outputtorque of −8.33 is achieved, corresponding to an engine torque of 1unit.

The third operating mode includes the “reverse and forward launch modes”(also referred to as “torque converter reverse and forward modes”)corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 1 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. InFIG. 1, this fraction is approximately 99%. The ratio of transmissionoutput speed to engine speed (transmission speed ratio) is approximately+/−0.001 (the positive sign indicates that the vehicle is creepingforward and negative sign indicates that the vehicle is creepingbackwards). Referring to FIG. 1 b, in the reverse and forward launchmodes, the clutch 55 is engaged. In the TC Reverse mode, themotor/generator 80 acts as a generator with −0.91 units of torque, themotor/generator 82 acts as a motor with −1.74 units of torque, and atorque ratio of −7.00 is achieved. In the TC Forward mode, themotor/generator 80 acts as a motor with −0.03 units of torque, themotor/generator 82 acts as a generator with 0.91 units of torque, and atorque ratio of 4.69 is achieved.

The fourth operating mode is a “continuously variable transmission rangemode” which includes the Range 1.1, Range 1.2, Range 1.3, Range 1.4,Range 2.1, Range 2.2, Range 2.3 and Range 2.4 operating pointscorresponding with rows 5-12 of each operating point table, such as thatof FIG. 1 b. In this mode, the EVT is driven by the engine as well asone of the motor/generators operating as a motor. The othermotor/generator operates as a generator and transfers 100% of thegenerated energy back to the motor. The operating points represented byRange 1.1, 1.2 . . . , etc. are discrete points in the continuum offorward speed ratios provided by the EVT. For example in FIG. 1 b, arange of torque ratios from 4.69 to 1.86 is achieved with the clutch 55engaged, and a range of ratios 1.36 to 0.54 is achieved with the clutch54 engaged.

The fifth operating mode includes the “fixed ratio” modes (F1, F2, F3and F4) corresponding with rows 13-16 of each operating mode table (i.e.operating mode table), such as that of FIG. 1 b. In this mode thetransmission operates like a conventional automatic transmission, withone or two torque transfer devices engaged to create a discretetransmission ratio. The clutching table accompanying each figure showsonly four fixed-ratio forward speeds but additional fixed ratios may beavailable. Referring to FIG. 1 b, in fixed ratio F1 the brake 57 isengaged to achieve a fixed torque ratio of 5.07. Accordingly, each “X”in the column of motor/generator 80, 82 in FIG. 1 b indicates that thebrake 56 or 57, respectively, is engaged and the motor/generator 80 or82 is not rotating. In fixed ratio F2, the clutches 52 and 55 areengaged to achieve a fixed ratio of 1.77. In fixed ratio F3, theclutches 50 and 54 are engaged to achieve a fixed ratio of 1.00. Infixed ratio F4, the brake 56 is engaged to achieve a fixed ratio of0.67.

The transmission 14 is capable of operating in so-called single or dualmodes. In single mode, the engaged torque transfer device remains thesame for the entire continuum of forward speed ratios (represented bythe discrete points: Ranges 1.1, 1.2, 1.3 and 1.4). In dual mode, theengaged torque transfer device is switched at some intermediate speedratio (e.g., Range 2.1 in FIG. 1). Depending on the mechanicalconfiguration, this change in torque transfer device engagement hasadvantages in reducing element speeds in the transmission.

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 1 b. FIG. 1 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 1 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 20; the N_(R2)/N_(S2) value is the tooth ratio of theplanetary gear set 30; and the N_(R3)/N_(S3) value is the tooth ratio ofthe planetary gear set 40. Also, the chart of FIG. 1 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 2.86, the step ratio between the second andthird fixed forward torque ratios is 1.77, the step ratio between thethird and fourth fixed forward torque ratios is 1.49, and the ratiospread is 7.57.

Description of a Second Exemplary Embodiment

With reference to FIG. 2 a, a powertrain 110 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral114. Transmission 114 is designed to receive at least a portion of itsdriving power from the engine 12.

In the embodiment depicted the engine 12 may also be a fossil fuelengine, such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM). As shown, the engine 12 has an outputshaft that serves as the input member 17 of the transmission 14. Atransient torque damper (not shown) may also be implemented between theengine 12 and the input member 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 114.An output member 19 of the transmission 114 is connected to a finaldrive 16.

The transmission 114 utilizes three differential gear sets, preferablyin the nature of planetary gear sets 120, 130 and 140. The planetarygear set 120 employs an outer gear member 124, typically designated asthe ring gear. The ring gear member 124 circumscribes an inner gearmember 122, typically designated as the sun gear. A carrier member 126rotatably supports a plurality of planet gears 127 such that each planetgear 127 meshingly engages both the outer, ring gear member 124 and theinner, sun gear member 122 of the first planetary gear set 120.

The planetary gear set 130 also has an outer gear member 134, often alsodesignated as the ring gear, that circumscribes an inner gear member132, also often designated as the sun gear. A plurality of planet gears137 are also rotatably mounted in a carrier member 136 such that eachplanet gear member 137 simultaneously, and meshingly, engages both theouter, ring gear member 134 and the inner, sun gear member 132 of theplanetary gear set 130.

The planetary gear set 140 also has an outer gear member 144, often alsodesignated as the ring gear, that circumscribes an inner gear member142, also often designated as the sun gear. A plurality of planet gears147 are also rotatably mounted in a carrier member 146 such that eachplanet gear member 147 simultaneously, and meshingly, engages both theouter, ring gear member 144 and the inner, sun gear member 142 of theplanetary gear set 140.

The transmission input member 17 is continuously connected with the sungear member 142 of the planetary gear set 140. The transmission outputmember 19 is connected with the carrier member 146 of the planetary gearset 140. A first interconnecting member 170 continuously connects thesun gear member 122 of the planetary gear set 120 with the sun gearmember 132 of the planetary gear set 130. A second interconnectingmember 172 continuously connects the carrier member 126 of the planetarygear set 120 with the ring gear member 144 of the planetary gear set140. A third interconnecting member 174 continuously connects thecarrier member 136 of the planetary gear set 130 with the sun gearmember 142 of the planetary gear set 140. A fourth interconnectingmember 176 continuously connects the ring gear member 124 of theplanetary gear set 120 with the transmission housing 160.

The transmission 114 also incorporates first and second motor/generators180 and 182, respectively. The stator of the first motor/generator 180is secured to the transmission housing 160. The rotor of the firstmotor/generator 180 is selectively connectable with the carrier member126 of the planetary gear set or the sun gear member 122 of theplanetary gear set 120 via engagement of clutch 154 or clutch 155,respectively.

The stator of the second motor/generator 182 is also secured to thetransmission housing 160. The rotor of the second motor/generator 182 issecured to the ring gear member 134 of the planetary gear set 130.

A first torque transfer device, such as clutch 150, selectively connectsthe sun gear member 132 with the carrier member 136. A second torquetransfer device, such as clutch 152, selectively connects the ring gearmember 144 of the planetary gear set 140 with the carrier member 146 ofthe planetary gear set 140. A third torque transfer device, such asclutch 154, selectively connects the carrier member 126 with themotor/generator 180. A fourth torque transfer device, such as the clutch155, selectively connects the sun gear member 122 of the planetary gearset 120 with the motor/generator 180. A fifth torque transmittingdevice, such as brake 156, selectively connects the carrier member 126with the transmission housing 160. A sixth torque transmitting device,such as the brake 157, is connected in parallel with the motor/generator182 for selectively braking rotation thereof. The first, second, third,fourth, fifth and sixth torque transfer devices 150, 152, 154, 155, 156and 157 are employed to assist in the selection of the operational modesof the hybrid transmission 114.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 2 a, that the transmission 114 selectively receives power fromthe engine 12. The hybrid transmission also exchanges power with anelectric power source 186, which is operably connected to a controller188. The electric power source 186 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

As described previously, each embodiment has sixteen functionalrequirements (corresponding with the 16 rows of each operating modetable shown in the Figures) which may be grouped into five operatingmodes. The first operating mode is the “battery reverse mode” whichcorresponds with the first row (Batt Rev) of the operating mode table ofFIG. 2 b. In this mode, the engine is off and the transmission elementconnected to the engine is effectively allowed to freewheel, subject toengine inertia torque. The EVT is driven by one of the motor/generatorsusing energy from the battery, causing the vehicle to move in reverse.The other motor/generator may or may not rotate in this mode. As shownin FIG. 2 b, in this mode the clutch 155 is engaged, the motor 180 has atorque of −1.19 units, the generator 182 has a torque of −1.00 units andan output torque of −4.33 is achieved, by way of example.

The second operating mode is the “EVT reverse mode” (or mechanicalreverse mode) which corresponds with the second row (EVT Rev) of theoperating mode table of FIG. 2 b. In this mode, the EVT is driven by theengine and by one of the motor/generators. The other motor/generatoroperates in generator mode and transfers 100% of the generated energyback to the driving motor. The net effect is to drive the vehicle inreverse. In this mode, the clutch 155 is engaged, the motor 180 has atorque of −2.06 units, the generator 182 has a torque of −2.17 units,and an output torque of −8.33 is achieved, corresponding to an inputtorque of 1 unit.

The third operating mode includes the “reverse and forward launch modes”corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 2 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. In TCRev, the clutch 155 is engaged, the motor/generator 180 acts as a motorwith −1.58 units of torque, the motor/generator 182 acts as a generatorwith −1.86 units of torque, and a torque ratio of −7.00 is achieved. InTC For, the clutch 155 is engaged, the motor/generator 180 acts as agenerator with 1.04 units of torque, the motor/generator 182 acts as amotor with 0.33 units of torque, and a torque ratio of 4.69 is achieved.For these torque ratios, approximately 99% of the generator energy isstored in the battery.

The fourth operating mode includes the “Range 1.1, Range 1.2, Range 1.3,Range 1.4, Range 2.1, Range 2.2, Range 2.3 and Range 2.4” modescorresponding with rows 5-12 of the operating mode table of FIG. 2 b. Inthis mode, the EVT is driven by the engine as well as one of themotor/generators operating as a motor. The other motor/generatoroperates as a generator and transfers 100% of the generated energy backto the motor. The operating points represented by Range 1.1, 1.2 . . . ,etc. are discrete points in the continuum of forward speed ratiosprovided by the EVT. For example in FIG. 2 b, a range of ratios from4.69 to 1.86 is achieved with the clutch 155 engaged, and a range ofratios from 1.36 to 0.54 is achieved with the clutch 154 engaged.

The fifth operating mode includes the fixed “ratio” modes (F1, F2, F3and F4) corresponding with rows 13-16 of the operating mode table ofFIG. 2 b. In this mode the transmission operates like a conventionalautomatic transmission, with two torque transfer devices engaged tocreate a discrete transmission ratio. In fixed ratio F1 the clutch 155and brake 156 are engaged to achieve a fixed ratio of 3.25. In fixedratio F2, the clutch 150 is engaged to achieve a fixed ratio of 1.98. Infixed ratio F3, the clutch 152 is engaged to achieve a fixed ratio of1.00. In fixed ratio F4, the brake 157 is engaged to achieve a fixedratio of 0.91.

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 2 b. FIG. 2 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 2 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 120; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 130; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 140. Also, the chart of FIG. 2 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.64, and the ratio spread is 3.57.

Description of a Third Exemplary Embodiment

With reference to FIG. 3 a, a powertrain 210 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral214. The transmission 214 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 214.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission 214.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member isoperatively connected to a planetary gear set in the transmission 214.An output member 19 of the transmission 214 is connected to a finaldrive 16.

The transmission 214 utilizes three differential gear sets, preferablyin the nature of planetary gear sets 220, 230 and 240. The planetarygear set 220 employs an outer gear member 224, typically designated asthe ring gear. The ring gear member 224 circumscribes an inner gearmember 222, typically designated as the sun gear. A carrier member 226rotatably supports a plurality of planet gears 227 such that each planetgear member 227 meshingly engages both the outer, ring gear member 224and the inner, sun gear member 222 of the first planetary gear set 220.

The planetary gear set 230 also has an outer ring gear member 234 thatcircumscribes an inner sun gear member 232. A plurality of planet gears237 are also rotatably mounted in a carrier member 236 such that eachplanet gear member 237 simultaneously, and meshingly, engages both theouter ring gear member 234 and the inner sun gear member 232 of theplanetary gear set 230.

The planetary gear set 240 also has an outer ring gear member 244 thatcircumscribes an inner sun gear member 242. A plurality of planet gears247 are rotatably mounted in a carrier member 246 such that each planetgear member 247 simultaneously and meshingly engages both the outer,ring gear member 244 and the inner, sun gear member 242 of the planetarygear set 240.

The transmission input member 17 is connected with the carrier member226. The transmission output member 19 is connected to the ring gearmember 244. A first interconnecting member 270 continuously connects thering gear member 224 with the carrier member 236. A secondinterconnecting member 272 connects the carrier member 226 with thecarrier member 246. A third interconnecting member 274 continuouslyconnects the ring gear member 234 with the sun gear member 242. A fourthinterconnecting member 276 connects the sun gear member 222 with thetransmission housing 260.

The transmission 214 also incorporates first and second motor/generators280 and 282, respectively. The stator of the first motor/generator 280is secured to the transmission housing 260. The rotor of the firstmotor/generator 280 is selectively connectable with the carrier member226 or the sun gear member 232 via engagement of the clutch 252 orclutch 254, respectively. The stator of the second motor/generator 282is also secured to the transmission housing 260. The rotor of the secondmotor/generator 282 is secured to the ring gear member 234.

A first torque-transfer device, such as clutch 250, selectively connectsthe carrier member 236 with the ring gear member 234. A secondtorque-transfer device, such as clutch 252, selectively connects thecarrier member 226 with the motor/generator 280. A third torquetransmitting device, such as clutch 254, selectively connects the sungear member 232 with the motor/generator 280. A fourth torquetransmitting device, such as brake 255, selectively connects the carriermember 236 with the transmission housing 260. A fifth torque transferdevice, such as the brake 256, is connected in parallel with themotor/generator 280 for selectively braking rotation thereof. A sixthtorque transmitting device, such as brake 257, is connected in parallelwith the motor/generator 282 for selectively braking rotation thereof.The first, second, third, fourth, fifth and sixth torque-transferdevices 250, 252, 254, 255, 256 and 257 are employed to assist in theselection of the operational modes of the hybrid transmission 214.

The hybrid transmission 214 receives power from the engine 12, and alsofrom electric power source 286, which is operably connected to acontroller 288.

The operating mode table of FIG. 3 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 214. These modes include the“battery reverse mode” (Batt Rev), “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “range 1.1, 1.2,1.3 . . . modes” and “fixed ratio modes” (F1, F2, F3 and F4) asdescribed previously.

As set forth above the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 3 b. FIG. 3 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 3 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 220; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 230; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 240. Also, the chart of FIG. 3 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between the first andsecond fixed forward torque ratios is 1.33, and the ratio spread is2.99.

Description of a Fourth Exemplary Embodiment

With reference to FIG. 4 a, a powertrain 310 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral314. The transmission 314 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 314. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 314.An output member 19 of the transmission 314 is connected to a finaldrive 16.

The transmission 314 utilizes three planetary gear sets 320, 330 and340. The planetary gear set 320 employs an outer ring gear member 324which circumscribes an inner sun gear member 322. A carrier member 326rotatably supports a plurality of planet gears 327 such that each planetgear 327 meshingly engages both the outer ring gear member 324 and theinner sun gear member 322 of the first planetary gear set 320.

The planetary gear set 330 also has an outer ring gear member 334 thatcircumscribes an inner sun gear member 332. A plurality of planet gears337 are also rotatably mounted in a carrier member 336 such that eachplanet gear member 337 simultaneously, and meshingly engages both theouter, ring gear member 334 and the inner, sun gear member 332 of theplanetary gear set 330.

The planetary gear set 340 also has an outer ring gear member 344 thatcircumscribes an inner sun gear member 342. A plurality of planet gears347 are also rotatably mounted in a carrier member 346 such that eachplanet gear member 347 simultaneously, and meshingly, engages both theouter ring gear member 344 and the inner sun gear member 342 of theplanetary gear set 340.

The transmission input member 17 is connected with the carrier member326. The transmission output member 19 is connected with the ring gearmember 344. A first interconnecting member 370 continuously connects thering gear member 324 with the carrier member 336. A secondinterconnecting member 372 continuously connects the carrier member 326with the carrier member 346. A third interconnecting member 374continuously connects the ring gear member 334 with the sun gear member342. A fourth interconnecting member 376 continuously connects the sungear member 322 with the transmission housing 360.

The transmission 314 also incorporates first and second motor/generators380 and 382, respectively. The stator of the first motor/generator 380is secured to the transmission housing 360. The rotor of the firstmotor/generator 380 is selectively connectable with the carrier member326 or the sun gear member 332 via the engagement of the clutch 352 orclutch 354 respectively. The stator of the second motor/generator 382 isalso secured to the transmission housing 360. The rotor of the secondmotor/generator 382 is secured to the ring gear member 334.

A first torque-transfer device, such as clutch 350, selectively connectsthe carrier member 336 with the ring gear member 334. A secondtorque-transfer device, such as clutch 352, selectively connects thecarrier member 326 with the motor/generator 380. A third torquetransmitting device, such as clutch 354, selectively connects the sungear member 332 with the motor/generator 380. A fourth torque-transferdevice, such as brake 355, selectively connects the carrier member 336with the transmission housing 360. A fifth torque transfer device, suchas the brake 356, is connected in parallel with the motor/generator 380for selectively braking rotation thereof. A sixth torque transmittingdevice, such as the brake 357, is connected in parallel with themotor/generator 382 for selectively braking rotation thereof. The first,second, third, fourth, fifth and sixth torque-transfer devices 350, 352,354, 355, 356 and 357 are employed to assist in the selection of theoperational modes of the transmission 314.

The hybrid transmission 314 receives power from the engine 12, and alsoexchanges power with an electric power source 386, which is operablyconnected to a controller 388.

The operating mode table of FIG. 4 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 314. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3 and F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 4 b. FIG. 4 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 4 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 320; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 330; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 340. Also, the chart of FIG. 4 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.24, and the ratio spread is 2.57.

Description of a Fifth Exemplary Embodiment

With reference to FIG. 5 a, a powertrain 410 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral414. The transmission 414 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 414. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 414.An output member 19 of the transmission 414 is connected to a finaldrive 16.

The transmission 414 utilizes three planetary gear sets 420, 430 and440. The planetary gear set 420 employs an outer ring gear member 424which circumscribes an inner sun gear member 422. A carrier member 426rotatably supports a plurality of planet gears 427 such that each planetgear 427 meshingly engages both the outer ring gear member 424 and theinner sun gear member 422 of the first planetary gear set 420.

The planetary gear set 430 also has an outer ring gear member 434 thatcircumscribes an inner sun gear member 432. A plurality of planet gears437 are also rotatably mounted in a carrier member 436 such that eachplanet gear member 437 simultaneously, and meshingly engages both theouter, ring gear member 434 and the inner, sun gear member 432 of theplanetary gear set 430.

The planetary gear set 440 also has an outer ring gear member 444 thatcircumscribes an inner sun gear member 442. A plurality of planet gears447 are also rotatably mounted in a carrier member 446 such that eachplanet gear member 447 simultaneously, and meshingly, engages both theouter ring gear member 444 and the inner sun gear member 442 of theplanetary gear set 440.

The transmission input member 17 is continuously connected with thecarrier member 436. The transmission output member 19 is continuouslyconnected with the carrier member 426. A first interconnecting member470 continuously connects the carrier member 426 with the ring gearmember 434. A second interconnecting member 472 continuously connectsthe sun gear member 422 with the carrier member 446. A thirdinterconnecting member 474 continuously connects the sun gear member 432with the sun gear member 442. A fourth interconnecting member 476continuously connects the ring gear member 424 with the transmissionhousing 460.

The transmission 414 also incorporates first and second motor/generators480 and 482, respectively. The stator of the first motor/generator 480is secured to the transmission housing 460. The rotor of the firstmotor/generator 480 is secured to the sun gear member 442. The stator ofthe second motor/generator 482 is also secured to the transmissionhousing 460. The rotor of the second motor/generator 482 is secured tothe ring gear member 444.

A first torque-transfer device, such as clutch 450, selectively connectsthe ring gear member 434 with the carrier member 436. A secondtorque-transfer device, such as clutch 452, selectively connects the sungear member 442 with the carrier member 446. A third torque transferdevice, such as the brake 456, is connected in parallel with themotor/generator 480 for selectively braking rotation thereof. A fourthtorque transmitting device, such as brake 457, is connected in parallelwith the motor/generator 482 for selectively braking rotation thereof.The first, second, third and fourth torque-transfer devices 450, 452,456 and 457 are employed to assist in the selection of the operationalmodes of the transmission 414.

The hybrid transmission 414 receives power from the engine 12 and alsofrom an electric power source 486, which is operably connected to acontroller 488.

The operating mode table of FIG. 5 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 414. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3 and F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 5 b. FIG. 5 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 5 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 420; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 430; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 440. Also, the chart of FIG. 5 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 2.21, and the ratio spread is 5.54.

Description of a Sixth Exemplary Embodiment

With reference to FIG. 6 a, a powertrain 510 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral514. The transmission 514 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 514. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 514.An output member 19 of the transmission 514 is connected to a finaldrive 16.

The transmission 514 utilizes three planetary gear sets 520, 530 and540. The planetary gear set 520 employs an outer ring gear member 524which circumscribes an inner sun gear member 522. A carrier member 526rotatably supports a plurality of planet gears 527 such that each planetgear 527 meshingly engages both the outer ring gear member 524 and theinner sun gear member 522 of the first planetary gear set 520.

The planetary gear set 530 also has an outer ring gear member 534 thatcircumscribes an inner sun gear member 532. A plurality of planet gears537 are also rotatably mounted in a carrier member 536 such that eachplanet gear member 537 simultaneously, and meshingly engages both theouter, ring gear member 534 and the inner, sun gear member 532 of theplanetary gear set 530.

The planetary gear set 540 also has an outer ring gear member 544 thatcircumscribes an inner sun gear member 542. A plurality of planet gears547 are also rotatably mounted in a carrier member 546 such that eachplanet gear member 547 simultaneously, and meshingly engages both theinner, sun gear member 542 and the outer, ring gear member 544 of theplanetary gear set 540.

The transmission input member 17 is continuously connected with thecarrier member 526. The transmission output member 19 is continuouslyconnected with the ring gear member 544. The first interconnectingmember 570 continuously connects the ring gear member 524 with thecarrier member 536. A second interconnecting member 572 continuouslyconnects the carrier member 526 with the carrier member 546. A thirdinterconnecting member 574 continuously connects the ring gear member534 with the sun gear member 542. A fourth interconnecting member 576continuously connects the sun gear member 522 with the transmissionhousing 560.

The transmission 514 also incorporates first and second motor/generators580 and 582, respectively. The stator of the first motor/generator 580is secured to the transmission housing 560. The rotor of the firstmotor/generator 580 is secured to the sun gear member 532. The stator ofthe second motor/generator 582 is also secured to the transmissionhousing 560. The rotor of the second motor/generator 582 is secured tothe ring gear member 534.

A first torque-transfer device, such as clutch 550, selectively connectsthe carrier member 536 with the ring gear member 534. A secondtorque-transfer device, such as clutch 552, selectively connects thecarrier member 526 with the sun gear member 532. A third torque transferdevice, such as the brake 556, is connected in parallel with themotor/generator 580 for selectively braking rotation thereof. A fourthtorque transmitting device, such as the brake 557, is connected inparallel with the motor/generator 582 for selectively braking rotationthereof. The first, second, third and fourth torque-transfer devices550, 552, 556 and 557 are employed to assist in the selection of theoperational modes of the hybrid transmission 514.

The hybrid transmission 514 receives power from the engine 12, and alsoexchanges power with an electric power source 586, which is operablyconnected to a controller 588.

The operating mode table of FIG. 6 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 514. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 6 b. FIG. 6 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 6 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 520; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 530; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 540. Also, the chart of FIG. 6 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.64, and the ratio spread is 3.88.

Description of a Seventh Exemplary Embodiment

With reference to FIG. 7 a, a powertrain 610 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral614. The transmission 614 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 614. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 614.An output member 19 of the transmission 614 is connected to a finaldrive 16.

The transmission 614 utilizes three planetary gear sets 620, 630 and640. The planetary gear set 620 employs an outer ring gear member 624which circumscribes an inner sun gear member 622. A carrier member 626rotatably supports a plurality of planet gears 627 such that each planetgear 627 meshingly engages both the outer ring gear member 624 and theinner sun gear member 622 of the first planetary gear set 620.

The planetary gear set 630 also has an outer ring gear member 634 thatcircumscribes an inner sun gear member 632. A plurality of planet gears637 are also rotatably mounted in a carrier member 636 such that eachplanet gear member 637 simultaneously, and meshingly engages both theouter, ring gear member 634 and the inner, sun gear member 632 of theplanetary gear set 630.

The planetary gear set 640 also has an outer ring gear member 644 thatcircumscribes an inner sun gear member 642. A plurality of planet gears647 are also rotatably mounted in a carrier member 646 such that eachplanet gear member 647 simultaneously, and meshingly, engages both theouter ring gear member 644 and the inner sun gear member 642 of theplanetary gear set 640.

The transmission input member 17 is continuously connected with thecarrier member 636. The transmission output member 19 is connected withthe carrier member 646. A first interconnecting member 670 continuouslyconnects the sun gear member 622 with the sun gear member 632. A secondinterconnecting member 672 continuously connects the carrier member 626with the ring gear member 644. A third interconnecting member 674continuously connects the ring gear member 634 with the carrier member646. A fourth interconnecting member 676 continuously connects the ringgear member 624 with the transmission housing 660.

The transmission 614 also incorporates first and second motor/generators680 and 682, respectively. The stator of the first motor/generator 680is secured to the transmission housing 660. The rotor of the firstmotor/generator 680 is secured to the sun gear member 622. The stator ofthe second motor/generator 682 is also secured to the transmissionhousing 660. The rotor of the second motor/generator 682 is secured tothe sun gear member 642.

A first torque-transfer device, such as clutch 650, selectively connectsthe sun gear member 632 with the carrier member 636. A second torquetransmitting device, such as clutch 652, selectively connects thecarrier member 626 with the carrier member 636. A third torquetransmitting device, such as brake 654, selectively connects the ringgear member 644 with the transmission housing 660. A fourth torquetransfer device, such as the brake 656, is connected in parallel withthe motor/generator 682 for selectively braking rotation thereof. Thefirst, second, third and fourth torque-transfer devices 650, 652, 654and 656 are employed to assist in the selection of the operational modesof the transmission 614.

The hybrid transmission 614 receives power from the engine 12, and alsoexchanges power with an electric power source 686, which is operablyconnected to a controller 688.

The operating mode table of FIG. 7 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 614. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 7 b. FIG. 7 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 7 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 620; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 630; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 640. Also, the chart of FIG. 7 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.94, and the ratio spread is 4.84.

Description of an Eighth Exemplary Embodiment

With reference to FIG. 8 a, a powertrain 710 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral714. The transmission 714 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 714. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 714.An output member 19 of the transmission 714 is connected to a finaldrive 16.

The transmission 714 utilizes three planetary gear sets 720, 730 and740. The planetary gear set 720 employs an outer ring gear member 724which circumscribes an inner sun gear member 722. A carrier member 726rotatably supports a plurality of planet gears 727 such that each planetgear 727 meshingly engages both the outer ring gear member 724 and theinner sun gear member 722 of the first planetary gear set 720.

The planetary gear set 730 also has an outer ring gear member 734 thatcircumscribes an inner sun gear member 732. A plurality of planet gears737 are also rotatably mounted in a carrier member 736 such that eachplanet gear member 737 simultaneously, and meshingly engages both theouter, ring gear member 734 and the inner, sun gear member 732 of theplanetary gear set 730.

The planetary gear set 740 also has an outer ring gear member 744 thatcircumscribes an inner sun gear member 742. A plurality of planet gears747 are also rotatably mounted in a carrier member 746 such that eachplanet gear member 747 simultaneously, and meshingly, engages both theouter ring gear member 744 and the inner sun gear member 742 of theplanetary gear set 740.

The transmission input member 17 is continuously connected with the sungear member 742. The transmission output member 19 is continuouslyconnected with the carrier member 746. A first interconnecting member770 continuously connects the sun gear member 722 with the sun gearmember 732. A second interconnecting member 772 continuously connectsthe carrier member 726 with the ring gear member 744. A thirdinterconnecting member 774 continuously connects the carrier member 736with the sun gear member 742. A fourth interconnecting member 776continuously connects the ring gear member 724 with the transmissionhousing 760.

The transmission 714 also incorporates first and second motor/generators780 and 782, respectively. The stator of the first motor/generator 780is secured to the transmission housing 760. The rotor of the firstmotor/generator 780 is secured to the sun gear member 722. The stator ofthe second motor/generator 782 is also secured to the transmissionhousing 760. The rotor of the second motor/generator 782 is secured tothe ring gear member 734.

A first torque-transfer device, such as clutch 750, selectively connectsthe sun gear member 732 with the carrier member 736. A second torquetransmitting device, such as clutch 752, selectively connects thecarrier member 746 with the ring gear member 744. A third torquetransfer device, such as the brake 754, selectively connects the carriermember 726 with the transmission housing 760. A fourth torquetransmitting device, such as the brake 756, is connected in parallelwith the motor/generator 782 for selectively braking rotation thereof.The first, second, third and fourth torque-transfer devices 750, 752,754 and 756 are employed to assist in the selection of the operationalmodes of the transmission 714.

The hybrid transmission 714 receives power from the engine 12 and alsofrom an electric power source 786, which is operably connected to acontroller 788.

The operating mode table of FIG. 8 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 714. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 8 b. FIG. 8 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 8 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 720; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 730; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 740. Also, the chart of FIG. 8 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.49, and the ratio spread is 2.92.

Description of a Ninth Exemplary Embodiment

With reference to FIG. 9 a, a powertrain 810 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral814. The transmission 814 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 814. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 814.An output member 19 of the transmission 814 is connected to a finaldrive 16.

The transmission 814 utilizes three planetary gear sets 820, 830 and840. The planetary gear set 820 employs an outer ring gear member 824which circumscribes an inner sun gear member 822. A plurality of planetgears 827 are also rotatably mounted in a carrier member 826 such thateach planet gear member 827 simultaneously, and meshingly engages boththe outer, ring gear member 824 and the inner, sun gear member 822 ofthe planetary gear set 820.

The planetary gear set 830 also has an outer ring gear member 834 thatcircumscribes an inner sun gear member 832. A plurality of planet gears837 are also rotatably mounted in a carrier member 836 such that eachplanet gear member 837 simultaneously, and meshingly engages both theouter, ring gear member 834 and the inner, sun gear member 832 of theplanetary gear set 830.

The planetary gear set 840 also has an outer ring gear member 844 thatcircumscribes an inner sun gear member 842. A plurality of planet gears847 are also rotatably mounted in a carrier member 846 such that eachplanet gear member 847 simultaneously, and meshingly engages both theouter, ring gear member 844 and the inner, sun gear member 842 of theplanetary gear set 840.

The transmission input member 17 is continuously connected with thecarrier member 836. The transmission output member 19 is continuouslyconnected with the carrier member 846. The first interconnecting member870 continuously connects the sun gear member 822 with the sun gearmember 832. A second interconnecting member 872 continuously connectsthe carrier member 826 with the ring gear member 844. A thirdinterconnecting member 874 continuously connects the ring gear member834 with the carrier member 846. A fourth interconnecting membercontinuously connects the ring gear member 824 with the transmissionhousing 860.

The transmission 814 also incorporates first and second motor/generators880 and 882, respectively. The stator of the first motor/generator 880is secured to the transmission housing 860. The rotor of the firstmotor/generator 880 is secured to the sun gear member 822. The stator ofthe second motor/generator 882 is also secured to the transmissionhousing 860. The rotor of the second motor/generator 882 is secured tothe sun gear member 842.

A first torque-transfer device, such as clutch 850, selectively connectsthe carrier member 826 with the ring gear member 834. A secondtorque-transfer device, such as clutch 852, selectively connects the sungear member 842 with the carrier member 846. A third torque-transferdevice, such as the brake 856, is connected in parallel with themotor/generator 880 for selectively braking rotation thereof. A fourthtorque transfer device, such as the brake 857, is connected in parallelwith the motor/generator 882 for selectively braking rotation thereof.The first, second, third and fourth torque-transfer devices 850, 852,856 and 857 are employed to assist in the selection of the operationalmodes of the hybrid transmission 814.

The hybrid transmission 814 receives power from the engine 12, and alsoexchanges power with an electric power source 886, which is operablyconnected to a controller 888.

The operating mode table of FIG. 9 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 814. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 9 b. FIG. 9 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 9 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 820; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 830; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 840. Also, the chart of FIG. 9 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.28, and the ratio spread is 3.62.

Description of a Tenth Exemplary Embodiment

With reference to FIG. 10 a, a powertrain 910 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral914. The transmission 914 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 914. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 914.An output member 19 of the transmission 914 is connected to a finaldrive 16.

The transmission 914 utilizes three planetary gear sets 920, 930 and940. The planetary gear set 920 employs an outer ring gear member 924which circumscribes an inner sun gear member 922. A carrier member 926rotatably supports a plurality of planet gears 927 such that each planetgear member 927 meshingly engages both the outer ring gear member 924and the inner sun gear member 922 of the first planetary gear set 920.

The planetary gear set 930 also has an outer ring gear member 934 thatcircumscribes an inner sun gear member 932. A plurality of planet gears937 are also rotatably mounted in a carrier member 936 such that eachplanet gear member 937 simultaneously, and meshingly engages both theouter, ring gear member 934 and the inner, sun gear member 932 of theplanetary gear set 930.

The planetary gear set 940 also has an outer ring gear member 944 thatcircumscribes an inner sun gear member 942. A plurality of planet gears947 are also rotatably mounted in a carrier member 946 such that eachplanet gear member 947 simultaneously, and meshingly engages both theouter, ring gear member 944 and the inner, sun gear member 942 of theplanetary gear set 940.

The transmission input member 17 is continuously connected with the sungear member 942. The transmission output member 19 is continuouslyconnected with the carrier member 946. The first interconnecting member970 continuously connects the sun gear member 922 with the sun gearmember 932. A second interconnecting member 972 continuously connectsthe carrier member 926 with the ring gear member 944. A thirdinterconnecting member 974 continuously connects the carrier member 936with the sun gear member 942. A fourth interconnecting member 976continuously connects the ring gear member 924 with the transmissionhousing 960.

The transmission 914 also incorporates first and second motor/generators980 and 982, respectively. The stator of the first motor/generator 980is secured to the transmission housing 960. The rotor of the firstmotor/generator 980 is secured to the sun gear member 922. The stator ofthe second motor/generator 982 is also secured to the transmissionhousing 960. The rotor of the second motor/generator 982 is secured tothe ring gear member 934.

A first torque-transfer device, such as clutch 950, selectively connectsthe sun gear member 932 with the carrier member 936. A secondtorque-transfer device, such as clutch 952, selectively connects thering gear member 944 with the carrier member 946. A third torquetransmitting device, such as the brake 954, selectively connects thecarrier member 926 with the transmission housing 960. A fourth torquetransfer device, such as the brake 956, is connected in parallel withthe motor/generator 982 for selectively braking rotation thereof. Thefirst, second, third and fourth torque-transfer devices 950, 952, 954and 956 are employed to assist in the selection of the operational modesof the hybrid transmission 914.

The hybrid transmission 914 receives power from the engine 12, and alsoexchanges power with an electric power source 986, which is operablyconnected to a controller 988.

The operating mode table of FIG. 10 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 914. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3 and F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 10 b. FIG. 10 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 10 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 920; the N_(R2)/N_(S2) value is the tooth ratioof the planetary gear set 930; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 940. Also, the chart of FIG. 10 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.62, and the ratio spread is 3.49.

Description of an Eleventh Exemplary Embodiment

With reference to FIG. 11 a, a powertrain 1010 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1014. The transmission 1014 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1014. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1014.An output member 19 of the transmission 1014 is connected to a finaldrive 16.

The transmission 1014 utilizes three planetary gear sets 1020, 1030 and1040. The planetary gear set 1020 employs an outer ring gear member 1024which circumscribes an inner sun gear member 1022. A carrier member 1026rotatably supports a plurality of planet gears 1027 such that eachplanet gear member 1027 meshingly engages both the outer ring gearmember 1024 and the inner sun gear member 1022 of the first planetarygear set 1020.

The planetary gear set 1030 also has an outer ring gear member 1034 thatcircumscribes an inner sun gear member 1032. A carrier member 1036rotatably supports a plurality of planet gears 1037 such that eachplanet gear member 1037 meshingly engages both the outer ring gearmember 1034 and the inner sun gear member 1032 of the planetary gear set1030.

The planetary gear set 1040 also has an outer ring gear member 1044 thatcircumscribes an inner sun gear member 1042. A carrier member 1046rotatably supports a plurality of planet gears 1047 such that eachplanet gear member 1047 meshingly engages both the outer ring gearmember 1044 and the inner sun gear member 1042 of the planetary gear set1040.

The transmission input member 17 is continuously connected with thecarrier member 1036. The transmission output member 19 is continuouslyconnected with the ring gear member 1044. The first interconnectingmember 1070 continuously connects the carrier member 1026 with the ringgear member 1034. A second interconnecting member 1072 continuouslyconnects the ring gear member 1024 with the sun gear member 1042. Athird interconnecting member 1074 continuously connects the carriermember 1036 with the carrier member 1046. A fourth interconnectingmember 1076 continuously connects the sun gear member 1022 with thetransmission housing 1060.

The transmission 1014 also incorporates first and secondmotor/generators 1080 and 1082, respectively. The stator of the firstmotor/generator 1080 is secured to the transmission housing 1060. Therotor of the first motor/generator 1080 is secured to the carrier member1026. The stator of the second motor/generator 1082 is also secured tothe transmission housing 1060. The rotor of the second motor/generator1082 is secured to the sun gear member 1032.

A first torque-transfer device, such as clutch 1050, selectivelyconnects the carrier member 1026 with the sun gear member 1032. A secondtorque-transfer device, such as clutch 1052, selectively connects thecarrier member 1046 with the ring gear member 1044. A third torquetransmitting device, such as brake 1054, selectively connects the ringgear member 1024 with the transmission housing 1060. A fourth torquetransfer device, such as the brake 1056, is connected in parallel withthe motor/generator 1082 for selectively braking rotation thereof. Thefirst, second, third and fourth torque-transfer devices 1050, 1052, 1054and 1056 are employed to assist in the selection of the operationalmodes of the hybrid transmission 1014.

The hybrid transmission 1014 receives power from the engine 12, and alsoexchanges power with an electric power source 1086, which is operablyconnected to a controller 1088.

The operating mode table of FIG. 11 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1014. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3 and F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 11 b. FIG. 11 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 11 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1020; the N_(R2)/N_(S2) value is the tooth ratioof the planetary gear set 1030; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 1040. Also, the chart of FIG. 11 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.80, and the ratio spread is 4.12.

Description of a Twelfth Exemplary Embodiment

With reference to FIG. 12 a, a powertrain 1110 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1114. The transmission 1114 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1114. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1114.An output member 19 of the transmission 1114 is connected to a finaldrive 16.

The transmission 1114 utilizes three planetary gear sets 1120, 1130 and1140. The planetary gear set 1120 has an outer ring gear member 1124that circumscribes an inner sun gear member 1122. A plurality of planetgears 1127 are rotatably mounted in a carrier member 1126 such that eachplanet gear member 1127 simultaneously, and meshingly engages both theouter, ring gear member 1124 and the inner, sun gear member 1122 of theplanetary gear set 1120.

The planetary gear set 1130 also has an outer ring gear member 1134 thatcircumscribes an inner sun gear member 1132. A plurality of planet gears1137 are also rotatably mounted in a carrier member 1136 such that eachplanet gear member 1137 simultaneously, and meshingly engages both theouter, ring gear member 1134 and the inner, sun gear member 1132 of theplanetary gear set 1130.

The planetary gear set 1140 also has an outer ring gear member 1144 thatcircumscribes an inner sun gear member 1142. A plurality of planet gears1147 are also rotatably mounted in a carrier member 1146 such that eachplanet gear member 1147 simultaneously, and meshingly engages both theouter, ring gear member 1144 and the inner, sun gear member 1142 of theplanetary gear set 1140.

The transmission input member 17 is continuously connected with the ringgear member 1124. The transmission output member 19 is continuouslyconnected with the carrier member 1136. A first interconnecting member1170 continuously connects the sun gear member 1122 with the sun gearmember 1132. A second interconnecting member 1172 continuously connectsthe carrier member 1126 with the carrier member 1146. A thirdinterconnecting member 1174 continuously connects the ring gear member1134 with the sun gear member 1142. A fourth interconnecting member 1176continuously connects the sun gear member 1122 with the transmissionhousing 1160.

The transmission 1114 also incorporates first and secondmotor/generators 1180 and 1182, respectively. The stator of the firstmotor/generator 1180 is secured to the transmission housing 1160. Therotor of the first motor/generator 1180 is secured to the sun gearmember 1142. The stator of the second motor/generator 1182 is alsosecured to the transmission housing 1160. The rotor of the secondmotor/generator 1182 is secured to the ring gear member 1144.

A first torque-transfer device, such as clutch 1150, selectivelyconnects the sun gear member 1142 with the carrier member 1146. A secondtorque transfer device, such as the brake 1156, is connected in parallelwith the motor/generator 1182 for selectively braking rotation thereof.The first and second torque-transfer devices 1150 and 1156 are employedto assist in the selection of the operational modes of the hybridtransmission 1114.

The hybrid transmission 1114 receives power from the engine 12, and alsoexchanges power with an electric power source 1186, which is operablyconnected to a controller 1188.

The operating mode table of FIG. 12 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1114. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 12 b. FIG. 12 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 12 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1120; the N_(R2)/N_(S2) value is the tooth ratioof the planetary gear set 1130; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 1140. Also, the chart of FIG. 12 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 3.01.

Description of a Thirteenth Exemplary Embodiment

With reference to FIG. 13 a, a powertrain 1210 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1214. The transmission 1214 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1214. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1214.An output member 19 of the transmission 1214 is connected to a finaldrive 16.

The transmission 1214 utilizes three planetary gear sets 1220, 1230 and1240. The planetary gear set 1220 employs an outer ring gear member 1224which circumscribes an inner sun gear member 1222. A carrier member 1226rotatably supports a plurality of planet gears 1227 such that eachplanet gear member 1227 meshingly engages both the outer ring gearmember 1224 and the inner sun gear member 1222 of the first planetarygear set 1220.

The planetary gear set 1230 also has an outer ring gear member 1234 thatcircumscribes an inner sun gear member 1232. A plurality of planet gears1237 are also rotatably mounted in a carrier member 1236 such that eachplanet gear member 1237 simultaneously, and meshingly engages both theouter, ring gear member 1234 and the inner, sun gear member 1232 of theplanetary gear set 1230.

The planetary gear set 1240 also has an outer ring gear member 1244 thatcircumscribes an inner sun gear member 1242. A plurality of planet gears1247 are also rotatably mounted in a carrier member 1246 such that eachplanet gear member 1247 simultaneously, and meshingly engages both theouter, ring gear member 1244 and the inner, sun gear member 1242 of theplanetary gear set 1240.

The transmission input member 17 is continuously connected with the ringgear member 1224. The transmission output member 19 is continuouslyconnected with the carrier member 1236. The first interconnecting member1270 continuously connects the sun gear member 1222 with the sun gearmember 1232. The second interconnecting member 1272 continuouslyconnects the carrier member 1226 with the carrier member 1246. The thirdinterconnecting member 1274 continuously connects the ring gear member1234 with the sun gear member 1242. The fourth interconnecting member1276 continuously connects the sun gear member 1222 with thetransmission housing 1260.

The transmission 1214 also incorporates first and secondmotor/generators 1280 and 1282, respectively. The stator of the firstmotor/generator 1280 is secured to the transmission housing 1260. Therotor of the first motor/generator 1280 is secured to the sun gearmember 1242.

The stator of the second motor/generator 1282 is also secured to thetransmission housing 1260. The rotor of the second motor/generator 1282is secured to the ring gear member 1244.

A first torque-transfer device, such as clutch 1250, selectivelyconnects the carrier member 1226 with the ring gear member 1234. Asecond torque transfer device, such as the brake 1256, is connected inparallel with the motor/generator 1282 for selectively braking rotationthereof. The first and second torque-transfer devices 1250 and 1256 areemployed to assist in the selection of the operational modes of thehybrid transmission 1214.

The hybrid transmission 1214 receives power from the engine 12, and alsoexchanges power with an electric power source 1286, which is operablyconnected to a controller 1288.

The operating mode table of FIG. 13 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1214. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 13 b. FIG. 13 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 13 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1220; the N_(R2)/N_(S2) value is the tooth ratioof the planetary gear set 1230; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 1240. Also, the chart of FIG. 13 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 2.09.

Description of a Fourteenth Exemplary Embodiment

With reference to FIG. 14 a, a powertrain 1310 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral1314. The transmission 1314 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 1314. A transient torque damper (notshown) may also be implemented between the engine 12 and the inputmember 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 1314.An output member 19 of the transmission 1314 is connected to a finaldrive 16.

The transmission 1314 utilizes three planetary gear sets 1320, 1330 and1340. The planetary gear set 1320 employs an outer ring gear member 1324which circumscribes an inner sun gear member 1322. A carrier member 1326rotatably supports a plurality of planet gears 1327 such that eachplanet gear member 1327 meshingly engages both the outer ring gearmember 1324 and the inner sun gear member 1322 of the first planetarygear set 1320.

The planetary gear set 1330 also has an outer ring gear member 1334 thatcircumscribes an inner sun gear member 1332. A plurality of planet gears1337, 1338 are also rotatably mounted in a carrier member 1336 such thateach planet gear member 1337 engages the outer, ring gear member 1334and each planet gear member 1338 simultaneously, and meshingly engagesboth the inner, sun gear member 1332 and the respective planet gearmember 1337.

The planetary gear set 1340 also has an outer ring gear member 1344 thatcircumscribes an inner sun gear member 1342. A plurality of planet gears1347 are also rotatably mounted in a carrier member 1346 such that eachplanet gear member 1347 simultaneously, and meshingly engages both theouter, ring gear member 1344 and the inner, sun gear member 1342 of theplanetary gear set 1340.

The transmission input member 17 is continuously connected with the ringgear member 1334. The transmission output member 19 is continuouslyconnected with the carrier member 1326. The first interconnecting member1370 continuously connects the carrier member 1326 with the carriermember 1336. The second interconnecting member 1372 continuouslyconnects the sun gear member 1322 with the carrier member 1346. Thethird interconnecting member 1374 continuously connects the sun gearmember 1332 with the sun gear member 1342. The fourth interconnectingmember 1376 continuously connects the ring gear member 1324 with thetransmission housing 1360.

The transmission 1314 also incorporates first and secondmotor/generators 1380 and 1382, respectively. The stator of the firstmotor/generator 1380 is secured to the transmission housing 1360. Therotor of the first motor/generator 1380 is secured to the sun gearmember 1342.

The stator of the second motor/generator 1382 is also secured to thetransmission housing 1360. The rotor of the second motor/generator 1382is selectively connectable with the carrier member 1346 or the ring gearmember 1344 via engagement of the clutch 1354 or clutch 1355,respectively.

A first torque-transfer device, such as clutch 1350, selectivelyconnects the carrier member 1326 with the ring gear member 1334. Asecond torque-transfer device, such as clutch 1352, selectively connectsthe carrier member 1346 with the sun gear member 1342. A third torquetransmitting device, such as clutch 1354, selectively connects thecarrier member 1346 with the motor/generator 1382. A fourth torquetransmitting device, such as clutch 1355, selectively connects the ringgear member 1344 with the motor/generator 1382. A fifth torque transferdevice, such as the brake 1356, is connected in parallel with themotor/generator 1380 for selectively braking rotation thereof. A sixthtorque transmitting device, such as the brake 1357, is connected inparallel with the motor/generator 1382 for selectively braking rotationthereof. The first, second, third, fourth, fifth and sixthtorque-transfer devices 1350, 1352, 1354, 1355, 1356 and 1357 areemployed to assist in the selection of the operational modes of thehybrid transmission 1314.

The hybrid transmission 1314 receives power from the engine 12, and alsoexchanges power with an electric power source 1386, which is operablyconnected to a controller 1388.

The operating mode table of FIG. 14 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 1314. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3 and F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 14 b. FIG. 14 b also provides an example of torque ratios thatare available utilizing the ring gear/sun gear tooth ratios given by wayof example in FIG. 14 b. The N_(R1)/N_(S1) value is the tooth ratio ofthe planetary gear set 1320; the N_(R2)/N_(S2) value is the tooth ratioof the planetary gear set 1330; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 1340. Also, the chart of FIG. 14 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 2.86, and the ratio spread is 7.57.

In the claims, the language “continuously connected” or “continuouslyconnecting” refers to a direct connection or a proportionally gearedconnection, such as gearing to an offset axis. Also, the “stationarymember” or “ground” may include the transmission housing (case) or anyother non-rotating component or components. Also, when a torquetransmitting mechanism is said to connect something to a member of agear set, it may also be connected to an interconnecting member whichconnects it with that member. It is further understood that differentfeatures from different embodiments of the invention may be combinedwithin the scope of the appended claims.

While various preferred embodiments of the present invention aredisclosed, it is to be understood that the concepts of the presentinvention are susceptible to numerous changes apparent to one skilled inthe art. Therefore, the scope of the present invention is not to belimited to the details shown and described but is intended to includeall variations and modifications which come within the scope of theappended claims.

1. An electrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; first, second and third differential gear sets eachhaving first, second and third members; said input member beingcontinuously connected with at least one member of said gear sets, andsaid output member being continuously connected with another member ofsaid gear sets; a first interconnecting member continuously connectingsaid first member of said first gear set with said first member of saidsecond gear set; a second interconnecting member continuously connectingsaid second member of said first gear set with said first member of saidthird gear set; a third interconnecting member continuously connectingsaid second member of said second gear set with said second member ofsaid third gear set; a fourth interconnecting member continuouslyconnecting a member of said first gear set with a stationary member;said first motor/generator being continuously connected with a member ofsaid first, second or third gear set; said second motor/generator beingcontinuously or selectively connected with a member of said second orthird gear set; a first torque transfer device selectively connecting amember of said first gear set with a member of said second gear set; anda second torque transmitting device connected in parallel with one ofsaid motor/generators for selectively preventing rotation thereof;wherein said first and second torque transfer devices are engagable toprovide an electrically variable transmission with a continuouslyvariable range of speed ratios and at least two fixed forward speedratios.
 2. The electrically variable transmission of claim 1, whereinsaid first, second and third differential gear sets are planetary gearsets.
 3. The electrically variable transmission of claim 2, whereincarrier members of each of said planetary gear sets are single-pinioncarrier members.
 4. The electrically variable transmission of claim 2,wherein at least one carrier member of said planetary gear sets is adouble-pinion carrier member.
 5. The electrically variable transmissionof claim 1, wherein said first and second torque transfer devices andsaid first and second motor/generators are operable to provide fiveoperating modes in the electrically variable transmission, includingbattery reverse mode, EVT reverse mode, reverse and forward launchmodes, continuously variable transmission range mode, and fixed ratiomode.
 6. The electrically variable transmission of claim 1, furthercomprising a third torque transmitting device selectively connecting amember of said second or third gear set with another member of saidthird gear set or with said stationary member.
 7. The electricallyvariable transmission of claim 6, further comprising a fourth torquetransmitting device selectively connecting a member of said first orthird gear set with said transmission housing.
 8. The electricallyvariable transmission of claim 6, further comprising a fourth torquetransmitting device connected in parallel with the other of saidmotor/generators for selectively preventing rotation thereof.
 9. Theelectrically variable transmission of claim 8, further comprising afifth and a sixth torque transmitting device selectively connectingmembers of said gear sets with said motor/generators.
 10. Anelectrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; first, second and third differential gear sets eachhaving first, second and third members; said input member beingcontinuously connected with at least one member of said gear sets, andsaid output member being continuously connected with another member ofsaid gear sets; a first interconnecting member continuously connectingsaid first member of said first gear set with said first member of saidsecond gear set; a second interconnecting member continuously connectingsaid second member of said first gear set with said first member of saidthird gear set; a third interconnecting member continuously connectingsaid second member of said second gear set with said second member ofsaid third gear set; a fourth interconnecting member continuouslyconnecting a member of said first gear set with said stationary member;said first motor/generator being selectively connected with a member ofsaid first, second or third gear set; said second motor/generator beingcontinuously connected with a member of said second or third gear set;and first, second and third torque transfer devices for selectivelyconnecting said members of said first, second or third gear sets with astationary member or with other members of said gear sets, said first,second and third torque transfer devices being engagable to provide anelectrically variable transmission with a continuously variable range ofspeed ratios and up to four fixed forward speed ratios between saidinput member and said output member.
 11. The electrically variabletransmission of claim 10, wherein said first, second and thirddifferential gear sets are planetary gear sets, and said first torquetransfer device selectively connects a member of said first gear setwith said a member of said second gear set.
 12. The electricallyvariable transmission of claim 11, wherein said second torquetransmitting device is connected in parallel with one of saidmotor/generators for selectively preventing rotation thereof.
 13. Theelectrically variable transmission of claim 12, wherein said thirdtorque transfer device selectively connects a member of said second orthird gear set with another member of said third gear set or with saidstationary member.
 14. The electrically variable transmission of claim13, further comprising: fourth and fifth torque transmitting devicesselectively connecting one of a pair of members of said first, second orthird gear set with one of said motor/generators.
 15. The electricallyvariable transmission of claim 14, further comprising a sixth torquetransmitting device connected in parallel with the other of saidmotor/generators for preventing rotation thereof.
 16. The electricallyvariable transmission of claim 11, wherein carrier members of each ofsaid planetary gear sets are single-pinion carrier members.
 17. Theelectrically variable transmission of claim 11, wherein at least onecarrier member of said planetary gear sets is a double-pinion carriermember.
 18. The electrically variable transmission of claim 15, whereinsaid first, second, third, fourth, fifth and sixth torque transferdevices are engagable to provide the electrically variable transmissionwith the continuously variable range of speed ratios and four fixedforward speed ratios.